The invention relates to a polymer for crosslinking an anti-reflective film that has a high refractive index and an anti-reflective composition containing the same that is particularly useful in an immersion lithography process using ArF (193 nm) of a semiconductor device manufacturing process.
In a process for forming ultra fine patterns, standing waves and reflective notching resulting from changes in optical properties and resist thicknesses of bottom films of photoresist films, and fluctuation of critical dimensions due to diffracted light and reflected light from the bottom films unavoidably occur. As a result, materials for absorbing light in wavelength range of the light used as an exposure light source have been used. Thus, an anti-reflective film for preventing reflection in bottom films may be deposited in a bottom portion of photoresist films, which can be used in a fine process.
From a light source, ultraviolet rays penetrate a photoresist film, so that a light incident on the bottom layer of the photoresist film is scattered or reflected. An organic anti-reflective film absorbs the scattered or reflected light, which affects the photolithography process.
A dry lithography process uses air having a re-fractive index of 1.0 as a medium for transmission of an exposure beam between an exposure lens and a wafer including a photoresist film. Unlike the dry lithography process, an immersion lithography process uses a liquid such as H2O or an organic solvent having a refractive index of 1.0 or more as a medium. As a result, even when a light source of the same wavelength is used, the immersion lithography process has the same effect as when a light source having a short wave or a lens having a high numerical aperture (NA) is used. Also, the depth of focus is not degraded.
Therefore, the immersion lithography process can improve the depth of focus, and form an ultra fine pattern using a conventional exposure wavelength.
However, when an anti-reflective composition having a low refractive index is used in the immersion lithography process, the reflectance of the exposure light source may increase, and the photoresist pattern may collapse. As a result, it is necessary to develop an anti-reflective material having a high refractive index useful for the immersion lithography process.